WEDNESDAY, Oct. 7, 2015 (HealthDay News) -- Overweight and mildly obese women with heart failure may live significantly longer than similarly heavy men with the progressive disease, a new study suggests.

These heavier women may also outlive normal-weight females with heart failure by as much as 16 percent, said lead researcher Dr. Leslie Cho, director of the Cleveland Clinic Women's Cardiovascular Center.

The bottom line: "It is not doomsday when an overweight or mildly obese patient, especially female, develops heart failure, as the prognosis may be quite good," said Dr. Carl Lavie, medical director of cardiac rehabilitation and prevention at the Ochsner Medical Center in New Orleans.

"There is an 'obesity paradox' in heart failure," said Lavie, who co-authored an editorial accompanying the study.

"Despite the adverse effects that overweight and obesity have on heart disease risk and on heart function, many studies, including several of my own, show that overweight and at least mildly obese patients with heart failure have a better short-term prognosis than do lean heart failure patients," he explained.

The study involved nearly 4,000 people with heart failure, a conditon where the heart doesn't pump blood the way it should. This potentially fatal disease affects about 5.7 million Americans, according to the American Heart Association.

The study results were published Oct. 7 in the journal JACC: Heart Failure.

Cho said the obesity paradox does seem real, but perhaps only for women in cases of heart failure.

On the one hand, overweight and obese men with heart failure should lose weight to improve heart function. On the other hand, women don't need to get to an ideal normal body weight, Cho said.

However, "the message is not that women with heart failure should go out and eat ice cream and gain a whole bunch of weight," she said.

Cho cautioned that this study only shows an association between weight and survival. It doesn't prove that being overweight is the reason for a woman with heart failure living longer.

While the mechanism behind the obesity paradox is unknown, Cho said it may be that women need more fatty acids than men for better heart function.

"We are just beginning to understand the difference gender makes in heart function," she said.

Lavie suggested that fitness, muscle mass and obesity severity also may play a role in the survival paradox.

For the study, Cho's team looked at medical records of more than 3,800 patients with heart failure.

Initially, the investigators noted an overweight advantage among men and women. But the men's survival benefit disappeared after taking into account factors such as smoking, diabetes and medications. Obesity and overweight actually shortened men's lives compared to normal-weight males with heart failure, the researchers said.

Women with the greatest survival advantage had a BMI (body mass index) of between 25 and 29.9, the researchers found. BMI is a calculation of body fat based on height and weight. A BMI over 25 is overweight; over 30 is considered obese.

Morbid obesity, a BMI of 40 or more, conferred no benefit, the researchers said.

Lavie said adults should strive to prevent heart failure in the first place. Maintaining a healthy weight is part of prevention, he said.

"Improving physical activity and fitness should be emphasized to prevent heart failure and improve its prognosis," Lavie said. Moderate and severe obesity need vigorous prevention and treatment, he added.